A variety of flocculants are used in the water treatment for municipal and industrial water as well as a variety waste water including sewage and waste water originating from chemical, metallurgical, dyeing, starch and other industries. Conventionally used for clarifying raw or waste water by separating suspended matter are inorganic flocculants such as ferrous sulfate, ferric sulfate, chlorinated copper as (Fe.sub.2 (SO.sub.4 ).sub.3.FeCl.sub.2), ferrous chloride, ferric chloride, alums, polymeric aluminum chloride and the like. Auxiliary flocculants are also used including slaked lime, activated silica, sodium silicate and bentonite.
JP-B-35012733 discloses the use of titanium chloride in the rapid clarification of waste water such as cellulose pulp-waste liquor and coal dressing-waste water. JP-A-49007178 discloses a flocculant composition containing aluminum sulfate and titanium sulfate. JP-A-56126483 discloses that dissolved phosphates in effluent are removed as precipitates by adding an aqueous composition containing ferrous sulfate, ferric sulfate, aluminum sulfate, magnesium sulfate and titanyl sulfate. JP-A-59049811 discloses a water processing method using titanium chloride, ferric chloride, ferric sulfate, aluminum sulfate and aluminum chloride either alone or in combination. JP-A-03213194 discloses that the flock-making efficiency of dyeing waste water is enhanced by combining an inorganic flocculant with an alkaline earth metal salt. JP-A-07108105 discloses water-blooming Microcystis and Anabaena cells growing in closed inland water are aggregated by treating the water with one or more inorganic salts selected from the group consisting of polymeric iron sulfate, polymeric iron chloride, ferric sulfate, ferric chloride, calcium chloride, magnesium chloride, magnesium sulfate, aluminum sulfate and aluminum chloride. Mizushori Gijitsu (Water treatment Technology) 5(12):15, 1964 reports the use of titanium chloride-base flocculant in the reduction of Fe contents in river water. It also reports that the iron-removing efficiency of titanium chloride is maximum in an acidic pH range between 3.5 and 5.5 but a soluble titanium compound remains in the supernatant.
Aluminum- and iron-based inorganic flocculants generally have an optimal flock-making pH range, namely neutral range for aluminum salts and acidic to neutral range for iron salts. In contrast, titanium salts have two optimal flock-making pH ranges, one in acidic side and the other in alkaline side separated by neutral range within which the titanium salt exhibits no or little flock-making function but is hydrolyzed into colloidal products. Accordingly, when attempting to clarify raw water including suspended clay particles with a titanium salt in the neutral pH range between 6 and 8, the titanium salt will hardly make coarse flocks of suspending matter but will remain in water mainly as a colloidal hydrolyzate which increases load to settling and filtering facilities. It is mainly for this reason that have precluded to date the use of titanium salts for producing municipal water in which water processing in the neutral pH range is essential.
A need exists for a titanium-based flocculant composition and a water processing method which can eliminate or alleviate various problems as discussed supra.